| 摘要 |
PURPOSE:To control the initial insensitive period in the beginning of ignition in safety by using a P-type combustion sensor which decreases in the electric resistance of its sensitive film as an air excess rate (lambda) increases. CONSTITUTION:A P-type oxide semiconductor element (S1) for gas detection formed by printing and baking an electrode film 2 on an insulating substrate 1 and providing a protective film 3 by coating the tip part with a P-type gas sensitive film by a plasma melt-spraying method is fitted to a combustor. The circuit composed of a negative characteristic thermistor S2, a capacitor (C) for a timer, a fixed resistance r1, an attraction type solenoid valve (G), a transistor (TR), an automatic reset key (K1) associated with the G, and a DC power source E is incorporated in the S1. When the K1 is closed, sufficient heating is not performed in the beginning of ignition and the resistance is large, but the TR is on and the G is therefore open because it is in the charging period of the C. If trouble such as extinction, wire breaking, deficiency in oxygen, incomplete combustion, overheating, and clogging in a heat exchange fin occurs, the TR is off and the G is closed after charging, but when there is no trouble, the S1 is heated in the charging period, so the TR is on and the G is open, thereby maintaining a normal combustion state.
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